As is well known, the basic components of a Linear Synchronous Motor (LSM) correspond to the standard rotor and stator components of an electric motor. Specifically, the operational interaction of these components are correspondingly similar. Unlike a standard electric motor, however, the components of an LSM are laid out substantially in-line. Such a configuration lends itself well for use as a propulsion unit for a vehicle that is designed to travel long distances (e.g. a train). For example, such a system might use a vehicle-based rotor, and a land-based stator.
Several advantages can be mentioned for using a hard wire, land-based stator as part of the propulsion unit for a long distance vehicle. For one, in general, the land-based stator will not be influenced by weather conditions or terrain variations (e.g. mountains and valleys) that might otherwise interfere with the reception of radiated signals. For another, it is not affected by vehicle travel through tunnels or other such obstructions. Moreover, by having a hard wire stator, it has been determined that an LSM can be made effectively impervious to electromagnetic interference (EMI) and noise.
Despite the many advantages that can be mentioned for an LSM, the motor has its sensitivities. In particular, it is also important to note that maintenance of the motor phase angle (i.e. the electrical phase angle between the vehicle-based rotor and the land-based stator) is crucial. Maximum thrust for a vehicle propelled by an LSM is achieved when the motor phase angle is maintained at ninety degrees (90°). Otherwise, motor operation can be significantly degraded, with unstable motor fluctuations and possible stoppage. The cure, however, is to have control over the spatial relationship between the rotor and the stator. Stated differently, it is necessary to know the position of the vehicle-based rotor (i.e. the vehicle itself), relative to the fixed, land-based stator.
In light of the above, it is an object of the present invention to provide a system and method for controlling movements of a vehicle along a land-based guideway, where the vehicle uses a propulsion unit (LSM) with its motor phase angle controlled by vehicle position. Another object of the present invention is to provide a system and method for controlling the motor phase angle of an LSM that is robust and can be used with either a wheeled or levitated vehicle. Still another object of the present invention is to provide a system and method for controlling the motor phase angle of an LSM that is reliable and resistant to high levels of wide band electromagnetic interference. Yet another object of the present invention is to provide a system for controlling movements of a vehicle along a land-based guideway that is relatively easy to manufacture, is simple to use and is comparatively cost effective.